Nanoclusters, including nanocrystals, are structures of a single chemical composition which are typically in the range of one to twenty-five nanometers in diameter. Nanoclusters are used as semiconductor memory storage elements and as optoelectronic devices for semiconductor applications.
When nanoclusters are embedded into a portion of an integrated circuit, the nanoclusters that are deposited in the periphery region have to be removed prior to the formation of peripheral devices. During deposition, nanoclusters of different sizes and shapes are formed. Some deposited nanoclusters are much larger than others while others are oblong in shape. The deposition of nanoclusters is not selective across a semiconductor substrate. Therefore, in some areas of an integrated circuit, the nanoclusters must be removed after the blanket deposition. The presence of random size distributions of nanoclusters is problematic as some nanoclusters are typically left in place when conventional etching processes are used. Even with tight nanocluster processing control that results in a narrow dispersion of cluster sizes, the presence of a few substantially larger clusters on the peripheral area is not statistically insignificant. When nanoclusters are deposited on a thin oxide surface, a long wet etch or dry etch is required to remove nanoclusters substantially larger than the mean size. This long wet or dry etch may compromise the integrity of devices built on the periphery. Selective removal of nanoclusters is therefore problematic.
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